Bone is a dynamic and continuously renewed tissue that undergoes significant modification throughout the life cycle. Bone remodeling integrates osteoblast-mediated bone formation and osteoclast-mediated bone resorption as well as osteocytes within the bone matrix and osteoblast-derived lining cells that cover the surface of bone (Crockett et al., 2011; Sims and Gooi, 2008). Disrupting the balance between bone resorption and formation leads to bone disorders such as osteoporosis, multiple myeloma, and osteopetrosis (Chen et al., 2018b; Feng and McDonald, 2011; Langdahl et al., 2016; Walsh and Gravallese, 2010). Osteoporosis is defined by the World Health Organization (WHO) as a ‘progressive systemic skeletal disease characterized by low bone mass and microarchitectural deterioration of bone tissue, with a consequent increase in bone fragility and susceptibility to fracture’ (Liu et al., 2019). It is estimated that osteoporosis has affected hundreds of millions of people worldwide, predominantly postmenopausal women (Brown, 2017; Compston et al., 2019). Pharmacological agents for the treatment of osteoporosis can be classified as either anabolic or antiresorptive, in the other words, either increasing bone building or blocking bone degradation (Compston et al., 2019; Liu et al., 2016a). However, treatment with anabolic agents such as parathyroid hormone (PTH) might lead to a simultaneous increase in bone resorption. For the antiresorptive agent bisphosphonates, a concomitant decrease in bone formation can be observed (Khosla and Hofbauer, 2017; Liu et al., 2018). These drawbacks of the current therapies might be attributed to one target for these drugs that fail to couple bone formation and resorption. Researchers are constantly striving to explore dual-action agents that modulate bone remodeling for the treatment of osteoporosis (Deal, 2009).

A large number of factors have been implicated in regulating bone formation, including Wnt/β-catenin signaling pathway, which is crucial for osteoblast proliferation, differentiation, and survival (Krishnan, 2006). Activation of the canonical Wnt/β-catenin signaling pathway involves recruitment of a degrading complex, stabilization of β-catenin, regulation of transcription factors such as Runx2 and Osterix, and activation of Wnt target genes (Baron and Kneissel, 2013; Karner and Long, 2017; Takada et al., 2009). This pathway is active in osteoprogenitor cells or preosteoblasts such as MC3T3-E1 cells, and many signaling molecules in this pathway are developed as drug targets (Bhukhai et al., 2012; Zhou et al., 2020). Osteoclasts, formed by the differentiation and fusion of hematopoietic mononuclear precursor cells under the stimulation of the receptor activator of nuclear factor-κB ligand (RANKL), are the only cells responsible for bone resorption. After binding to receptor RANK, RANKL promotes osteoclastogenesis by activating several signaling pathways, including nuclear factor of activated T cells, cytoplasmic 1 (NFATc1)/c-fos pathways (Kim and Kim, 2016; Zhao et al., 2017). Furthermore, several genes such as cathepsin K, matrix metalloprotein-9 (MMP-9), and tartrate-resistant acid phosphatase (TRAP) that governing osteoclast differentiation and function are triggered after RANKL/RANK signal transduction cascades (Boyle et al., 2003; Jiang et al., 2019).

Brain-derived neurotrophic factor (BDNF) is a member of the neurotrophin family that regulates a variety of biological processes predominantly via binding to the transmembrane receptor tyrosine kinase B (TrkB). Nonetheless, BDNF-elicited TrkB signals are transient with a peak signal at 10 min and decreases at 60 min (Liu et al., 2016a; Liu et al., 2014). A systemic application study of BDNF found that BDNF had a short half-life and did not readily cross the blood-brain barrier (Felts et al., 2002). The outcomes of several clinical trials using recombinant BDNF are also disappointing, possibly because of the short in vivo half-life and poor delivery of BDNF (Ochs et al., 2000; Thoenen and Sendtner, 2002). These drawbacks impose an insurmountable hurdle to clinical application of BDNF. 7,8-Dihydroxyflavone (7,8-DHF), a plant-derived flavonoid, has been reported to overcome the above limitations of BDNF and identified as a functional BDNF mimic, which is able to induce TrkB dimerization and activate its downstream signaling molecules (Jang et al., 2010). 7,8-DHF is now extensively validated in various biochemical and cellular systems. It has been shown that BDNF could promote osteoblast differentiation, migration, and fracture healing (Kilian et al., 2014; Liu et al., 2018; Zhang et al., 2020; Zhang et al., 2017). Recently, we found that 7,8-DHF at the dose of 10 mg/kg·BW resulted in a marked increase in bone mineral density (BMD) irrespective of dietary conditions in female mice (Zhao et al., 2021). Inspired by the studies above, we wonder if 7,8-DHF could serve as a regulator on bone remodeling and exert antiosteoporosis effects. What’s more, it is of interest to explore whether TrkB mediates the interaction between 7,8-DHF-induced osteoblastogenesis and Wnt/β-catenin signaling. In this study, we attempted to investigate the effects of BDNF and 7,8-DHF on osteoblastogenesis in osteoprogenitor MC3T3-E1 cells and on RANKL-induced osteoclastogenesis in RAW264.7 cells in vitro, particularly to elucidate the molecular mechanisms underlying functions of 7,8-DHF. In addition, the in vivo effects of 7,8-DHF on bone remodeling were examined in an ovariectomy (OVX)-induced osteoporosis rat model.

In this study, we performed a series of studies in vitro to demonstrate that 7,8-DHF promoted osteoblastic differentiation by interacting with TrkB receptors and subsequently reinforcing the Wnt/β-catenin pathway in MC3T3-E1 cells. In addition, 7,8-DHF inhibited RANKL-induced osteoclastogenesis by suppressing c-fos in RAW264.7 cells. Moreover, the effects of 7,8-DHF in vivo were explored through an OVX-induced bone-loss rat model. Results indicated that 5 mg/kg/day 7,8-DHF could improve the bone mass, microarchitecture, and bone strength of the OVX rat by inhibiting bone resorption and enhancing bone formation in vivo. Thus, our study demonstrates that 7,8-DHF could be an attractive therapeutic agent for osteoporosis treatment (Figure 7).

Figure 7

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7,8-DHF has been identified as a promising small-molecular BDNF mimetic compound, which mimics the physiological actions of BDNF via directly binding to the extracellular domain of TrkB to trigger TrkB receptor dimerization and autophosphorylation (Jang et al., 2010). 7,8-DHF has been broadly validated in various BDNF-implicated disease models including a variety of neurological diseases, mental diseases, metabolic diseases, and obesity (Agrawal et al., 2015; Bollen et al., 2012; Chen et al., 2019; Liu et al., 2016b; Pandey et al., 2020; Zhang et al., 2014). Especially, 7,8-DHF displays robust therapeutic efficacy toward Alzheimer’s disease (AD) (Gao et al., 2016; Zhang et al., 2014). At present, there are few related studies having been done on the physiological, pharmacological, and functional activities of 7,8-DHF on osteolytic disease, for example, osteoporosis. In fact, recent studies reveal the important roles of BDNF in fracture healing. As early as in 2000, BDNF and TrkB were firstly found in bone-forming cells of mice, suggesting that they were involved in the regulation of bone formation as an autocrine and paracrine factor in vivo (Asaumi et al., 2000). In 2014, the detection of BDNF and TrkB in human fracture gap tissue during various stages of the bone formation process was reported (Kilian et al., 2014). Afterward, some researches confirmed that BDNF plays a positive role in accelerating bone union (Kauschke et al., 2018a; Kauschke et al., 2018b; Liu et al., 2018). Recently, a study provided further understanding for the underlying mechanism of BDNF in fracture healing that BDNF contributed to MC3T3-E1 migration and increased the expression level of integrin β1 (Zhang et al., 2020). Considering the fact that 7,8-DHF mimics so many aspects of BDNF, we hypothesized that there may be a regulatory network involving 7,8-DHF and bone remodeling. To our knowledge, this is the first study reporting the therapeutic potential of 7,8-DHF toward osteoporosis.

Bone homeostasis requires the coordinated recruitment of osteoblasts and osteoclasts to sites of remodeling (Phan et al., 2020). The crosstalk among bone cells is maintained and orchestrated by a complex system, which includes hormones, growth factors, and physical activity (Jiang et al., 2019). Due to the tight coupling and synchronization of bone formation and resorption, the limitation of clinically used drugs is stimulation or inhibition of both phases at the same time. For example, bisphosphonates decrease bone degradation, but also reduce bone formation. What’s worse, it may cause serious jaw and subtrochanteric fractures, which are mostly attributed to its effects that induce osteoclast cytotoxicity (Gasser, 2019; Khosla and Hofbauer, 2017; Reid, 2011). Likewise, drugs such as PTH or PTH-related protein mainly enhance the bone formation and meanwhile stimulate bone resorption (Leder, 2017). In our present study, 7,8-DHF, as well as BDNF, exhibited the ability to regulate bone remodeling by synchronously promoting osteoblastic differentiation and restraining the formation of osteoclasts. Previous studies reported that BDNF is a potential osteoclastogenic factor in multiple myeloma, and myeloma-derived BDNF could promote RANKL secretion and osteoclasts formation (Ai et al., 2012; Sun et al., 2012). Nevertheless, in our study we found that BNDF at the concentration of 25 ng/mL markedly inhibited the formation of TRAP-positive multinucleated osteoclasts derived from RAW264.7 cells, though contributed to the growth of RAW264.7 cells. Of note, we observed that the TRAP-positive cells, c-fos mRNA level, the expression of MMP-9, and Adamts5 were decreased when 0.5 or 1 μM 7,8-DHF was used, while the inhibitory effect was lost at dose of 5 μM. This observation indicated that the effective therapeutic dose range of 7,8-DHF for suppression of bone resorption might be narrow. The underlying molecular mechanism accounting for this curve remains unclear. Nevertheless, the prodrug of 7,8-DHF, R13, also displayed the similar bell-shaped pharmacological curve in therapeutic treating AD (Chen et al., 2018a). Therefore, optimization of the chemical structure of 7,8-DHF or development of its analogues might exhibit a positive dose-dependent effect, extending the inhibitory activity for osteoclastogenesis.

Besides 7,8-DHF, other natural products or their derivatives such as emodin, wedelolactone, rhein, and psoralen have also showed dual effects on bone remodeling (Jiang et al., 2019; Kim et al., 2014; Liu et al., 2016a; Newman and Cragg, 2020; Zhang et al., 2019). One of the possible causes of their dual effects might result from that they can target multiple signaling pathways and display various beneficial pharmacological effects (Jiang et al., 2019). The canonical Wnt/β-catenin signaling pathway has been demonstrated to be responsible for a variety of biological processes, including the regulation of osteoblast proliferation and differentiation. β-Catenin is the principal mediator of Wnt/β-catenin signaling pathway (Baron and Kneissel, 2013; Gordon and Nusse, 2006). In the absence of extracellular Wnt ligands, β-catenin is recruited into a degrading complex comprising GSK-3β, the scaffold protein axin, and adenomatous polyposis coli (Moon et al., 2004). Thus, the content of the β-catenin protein in normal cells is generally kept very low. In the presence of Wnt ligands, on the other hand, GSK3β is phosphorylated to yield inactive p-GSK3β, and the degrading complex is depolymerized, which allows β-catenin to avoid the degradation by the proteasome and accumulate in the cytoplasm (Chen et al., 2021; Wang et al., 2019). The accumulated β-catenin translocates into the nucleus, binds with T-cell-specific transcription factor/lymphoid enhancer binding factor, and activates a series of target gene, such as cyclin D1, Runx2, and Osterix. It has been reported that BDNF is involved in the regulation of GSK3β activity both in the retina tissue in vivo and in the neuronal cells in vitro (Gupta et al., 2014). In this research, we observed that 7,8-DHF induced phosphorylation of GSK3β at the serine nine residue, thus promoting the aggregation and localization of β-catenin in the nucleus.

Cyclin D1, whose activity is required for G1/S transition, is one of the key cell cycle regulators. It is synthesized during G1 phase and assembles with either cyclin-dependent kinase 4 (CDK4) or CDK6 (Fujita et al., 2002; Ozaki et al., 2007). Treatment of MC3T3-E1 cells with 7,8-DHF could up-regulate the mRNA level of cyclin D1, thus stimulating more cells at S phase but less at G0/G1 phase. These results indicated active DNA synthesis, which was consistent with cell proliferation results. Two transcription factors, Runx2 and Osterix/SP7, have previously been shown to be essential for the differentiation of osteoblasts (Ryoo et al., 2006; Yang and Karsenty, 2002). Runx2 not only acts as a scaffold for nucleic acids and regulatory factors involved in skeletal gene expression, but also promotes skeletal development on different levels, including differentiation of mesenchymal progenitors into osteoblasts, chondrocyte maturation, and skeletal morphogenesis (Kokabu et al., 2016; McGee-Lawrence et al., 2014). Osterix plays an important role at a later step in the process of osteoblast differentiation, that is, the differentiation of pre-osteoblasts into mature osteoblasts and osteocytes. Moreover, it is a key target of mechanical signals that affect bone biology (Fan et al., 2007). In the present study, we have shown that 7,8-DHF could enhance osteoblastic differentiation by stimulating Runx2 and Osterix via β-catenin. The possibility that 7,8-DHF enhanced the activity of other Runx2 inducers such as Smad2 and TAK1 was excluded.

What molecule(s) served as a ‘bridge’ between 7,8-DHF-induced osteogenesis and the activation of the Wnt/β-catenin pathway? It has been reported that 7,8-DHF inhibits obesity through activating muscular TrkB. The anti-obesity activity of 7,8-DHF is muscular TrkB-dependent and 7,8-DHF cannot mitigate diet-induced obesity in female muscle-specific TrkB-knockout mice (Chan et al., 2015). Besides, the promotion effect of BDNF on osteoblast migration and fracture healing is also via TrkB. The specific inhibitor for Trks, K252a, can suppress BDNF-induced cell migration, integrin β1 expression, and activation of ERK1/2 and AKT signaling pathways (Zhang et al., 2020). We thus hypothesized that TrkB is the link between 7,8-DHF and Wnt/β-catenin reinforcement during osteogenic differentiation. As expected, 7,8-DHF-induced activation of Wnt/β-catenin signaling pathway in MC3T3-E1 cells was diminished by inhibiting TrkB with K252a. In the presence of K252a, the elevation of the expression of p-GSK3β, β-catenin, Runx2, and Osterix was reduced, suggesting that 7,8-DHF acts on TrkB to alter the expression of critical genes involved in the Wnt/β-catenin signaling pathway.

Differentiated osteoblasts subsequently produce positive and negative regulators of osteoclastogenesis, such as RANKL, a member of the tumor necrosis factor-ligand family, and its natural decoy receptor OPG, respectively (Kong et al., 1999; Lacey et al., 1998). RANKL binds to its receptor RANK on osteoclast progenitors and activates c-fos to induce transcription of genes related to osteoclasts (Leibbrandt and Penninger, 2008). Whereas OPG competitively binds to RANKL and prevents activation of RANK, leading to the inhibition of osteoclast recruitment. Otherwise, the production of OPG is tightly dependent on the Wnt/β-catenin signaling pathway (Li et al., 2020). From the experimental results, we infer that 7,8-DHF-induced increase of OPG might be involved in the activation of Wnt/β-catenin signaling pathway, and the decreased RANKL probably down-regulated the transcription of c-fos to a certain degree, leading to the suppression of NF-κB pathway and ultimately inhibiting the osteoclastic differentiation of RAW264.7 cells. The RANK/RANKL/OPG axes couple osteoblast and osteoclast activities, thereby controlling the balance between bone formation and resorption (Boyle et al., 2003). The ratio between OPG and RANKL is considered a quantitative osteogenic activity standard (Liu et al., 2012). The current study suggests that 7,8-DHF positively modulates OPG/RANKL balance, as OPG/RANKL ratio was increased in response to 7,8-DHF, representing the capability of 7,8-DHF to inhibit osteoclast activity.

Considering the fascinating dual functional effect of 7,8-DHF on osteoblasts and osteoclasts in vitro, we further proved that 7,8-DHF exerted a protective effect against osteoporosis in vivo using an OVX-induced osteoporotic rat model. In agreement with the previous observations, ovarian hormone deficiency, caused by surgical removal of ovaries, significantly increased body weight (Zhao et al., 2019; Zhou et al., 2020), but this excess body weight gain was partially prevented by 7,8-DHF. Besides, OVX can accelerate bone remodeling, an uncoupling between bone resorption and formation (Libouban et al., 2003). As the resorption phase is short but the period required for osteoblastic replacement is long, any increase in the rate of bone remodeling will result in a loss of bone mass (Raisz, 2005). It is necessary to evaluate the true impact of a treatment on the quality of trabecular bone because trabecular bone is more readily lost due to OVX in this animal model (Maïmoun et al., 2012). Radiographic and histomorphology analysis showed that 7,8-DHF attenuated bone loss and alleviated the compromised trabecular microstructure in ovariectomized rat. However, neither of the doses was able to restore trabecular bone completely. The loss of bone mass is usually accompanied by enhanced levels of the bone turnover markers, such as ALP and BGP (Park et al., 2011). The relief of the high bone turnover status in the 7,8-DHF-treated groups was evidenced by lower serum levels of ALP and BGP. Moreover, an increase in urinary calcium excretions might contribute to the reduction of BMD (Park et al., 2011). Results showed that 7,8-DHF prevented the OVX-induced increase in urinary Ca excretion. Although such inhibition generally would be considered beneficial, biomechanical properties of bone may be decreased if bone remodeling is inhibited excessively. Fortunately, we found that 7,8-DHF at a lower dose (5 mg/kg/day) significantly improved the biomechanical parameters in OVX rats.

In summary, the present study evaluates the potential of 7,8-DHF as a novel dual regulator for bone formation and bone resorption. We found that 7,8-DHF promoted osteoblastic proliferation and differentiation through the TrkB-Wnt/β-catenin signaling pathway and inhibited osteoclastogenesis at the same time. Furthermore, 7,8-DHF could alleviate osteoporosis phenotypes, enhance mechanical properties, and ameliorate bone remodeling in OVX rat. Notably, 7,8-DHF is orally bioactive and is safe for chronic treatment. Hence, it acts as a good compound for further medicinal application to maximize its therapeutic properties toward various bone disorders, especially postmenopausal osteoporosis.

All data generated or analysed during this study are included in the manuscript and supporting files.

1. 1. Agrawal R
   2. Noble E
   3. Tyagi E
   4. Zhuang Y
   5. Ying Z
   6. Gomez-Pinilla F

   (2015) Flavonoid derivative 7,8-DHF attenuates TBI pathology via TrkB activation

   Biochimica Et Biophysica Acta (BBA) - Molecular Basis of Disease 1852:862–872.

   https://doi.org/10.1016/j.bbadis.2015.01.018

   • Google Scholar
2. 1. Ai LS
   2. Sun CY
   3. Zhang L
   4. Zhou SC
   5. Chu ZB
   6. Qin Y
   7. Wang YD
   8. Zeng W
   9. Yan H
   10. Guo T
   11. Chen L
   12. Yang D
   13. Hu Y

   (2012) Inhibition of BDNF in multiple myeloma blocks osteoclastogenesis via Down-Regulated Stroma-Derived RANKL expression both in vitro and in vivo

   PLOS ONE 7:e46287.

   https://doi.org/10.1371/journal.pone.0046287

   • PubMed
   • Google Scholar
3. 1. Asaumi K
   2. Nakanishi T
   3. Asahara H
   4. Inoue H
   5. Takigawa M

   (2000) Expression of neurotrophins and their receptors (TRK) during fracture healing

   Bone 26:625–633.

   https://doi.org/10.1016/S8756-3282(00)00281-7

   • PubMed
   • Google Scholar
4. 1. Baron R
   2. Kneissel M

   (2013) WNT signaling in bone homeostasis and disease: from human mutations to treatments

   Nature Medicine 19:179–192.

   https://doi.org/10.1038/nm.3074

   • PubMed
   • Google Scholar
5. 1. Bhukhai K
   2. Suksen K
   3. Bhummaphan N
   4. Janjorn K
   5. Thongon N
   6. Tantikanlayaporn D
   7. Piyachaturawat P
   8. Suksamrarn A
   9. Chairoungdua A

   (2012) A phytoestrogen diarylheptanoid mediates estrogen receptor/Akt/Glycogen synthase kinase 3β Protein-dependent activation of the wnt/β-Catenin signaling pathway

   Journal of Biological Chemistry 287:36168–36178.

   https://doi.org/10.1074/jbc.M112.344747

   • Google Scholar
6. 1. Blainey P
   2. Krzywinski M
   3. Altman N

   (2014) Replication

   Nature Methods 11:879–880.

   https://doi.org/10.1038/nmeth.3091

   • Google Scholar
7. 1. Bollen E
   2. Akkerman S
   3. Steinbusch HWM
   4. Prickaerts J

   (2012) P.2.019 BDNF/TrkB signaling in learning and memory: the effects of 7,8-dihydroxyflavone on object memory

   European Neuropsychopharmacology 22:S47–S48.

   https://doi.org/10.1016/S0924-977X(12)70051-2

   • Google Scholar
8. 1. Boyle WJ
   2. Simonet WS
   3. Lacey DL

   (2003) Osteoclast differentiation and activation

   Nature 423:337–342.

   https://doi.org/10.1038/nature01658

   • PubMed
   • Google Scholar
9. 1. Brown C

   (2017) Staying strong

   Nature 550:S15–S17.

   https://doi.org/10.1038/550S15a

   • Google Scholar
10. 1. Chan CB
    2. Tse MC
    3. Liu X
    4. Zhang S
    5. Schmidt R
    6. Otten R
    7. Liu L
    8. Ye K

    (2015) Activation of muscular TrkB by its small molecular agonist 7,8-dihydroxyflavone sex-dependently regulates energy metabolism in diet-induced obese mice

    Chemistry & Biology 22:355–368.

    https://doi.org/10.1016/j.chembiol.2015.02.003

    • PubMed
    • Google Scholar
11. 1. Chen C
    2. Wang Z
    3. Zhang Z
    4. Liu X
    5. Kang SS
    6. Zhang Y
    7. Ye K

    (2018a) The prodrug of 7,8-dihydroxyflavone development and therapeutic efficacy for treating Alzheimer's disease

    PNAS 115:578–583.

    https://doi.org/10.1073/pnas.1718683115

    • PubMed
    • Google Scholar
12. 1. Chen X
    2. Wang Z
    3. Duan N
    4. Zhu G
    5. Schwarz EM
    6. Xie C

    (2018b) Osteoblast-osteoclast interactions

    Connective Tissue Research 59:99–107.

    https://doi.org/10.1080/03008207.2017.1290085

    • PubMed
    • Google Scholar
13. 1. Chen Y
    2. Xue F
    3. Xia G
    4. Zhao Z
    5. Chen C
    6. Li Y
    7. Zhang Y

    (2019) Transepithelial transport mechanisms of 7,8-dihydroxyflavone, a small molecular TrkB receptor agonist, in human intestinal Caco-2 cells

    Food & Function 10:5215–5227.

    https://doi.org/10.1039/C9FO01007F

    • Google Scholar
14. 1. Chen X
    2. Liu Y
    3. Meng B
    4. Wu D
    5. Wu Y
    6. Cao Y

    (2021) Interleukin-20 inhibits the osteogenic differentiation of MC3T3-E1 cells via the GSK3β/β-catenin signalling pathway

    Archives of Oral Biology 125:105111.

    https://doi.org/10.1016/j.archoralbio.2021.105111

    • PubMed
    • Google Scholar
15. 1. Compston JE
    2. McClung MR
    3. Leslie WD

    (2019) Osteoporosis

    The Lancet 393:364–376.

    https://doi.org/10.1016/S0140-6736(18)32112-3

    • PubMed
    • Google Scholar
16. 1. Crockett JC
    2. Rogers MJ
    3. Coxon FP
    4. Hocking LJ
    5. Helfrich MH

    (2011) Bone remodelling at a glance

    Journal of Cell Science 124:991–998.

    https://doi.org/10.1242/jcs.063032

    • PubMed
    • Google Scholar
17. 1. Deal C

    (2009) Potential new drug targets for osteoporosis

    Nature Clinical Practice Rheumatology 5:20–27.

    https://doi.org/10.1038/ncprheum0977

    • Google Scholar
18. 1. Fan D
    2. Chen Z
    3. Wang D
    4. Guo Z
    5. Qiang Q
    6. Shang Y

    (2007) Osterix is a key target for mechanical signals in human thoracic ligament flavum cells

    Journal of Cellular Physiology 211:577–584.

    https://doi.org/10.1002/jcp.21016

    • PubMed
    • Google Scholar
19. 1. Felts PA
    2. Smith KJ
    3. Gregson NA
    4. Hughes RA

    (2002) Brain-derived neurotrophic factor in experimental autoimmune neuritis

    Journal of Neuroimmunology 124:62–69.

    https://doi.org/10.1016/S0165-5728(02)00017-6

    • PubMed
    • Google Scholar
20. Book

    1. Feng X
    2. McDonald JM

    (2011)

    Disorders of Bone Remodeling

    In: Abbas AK, Galli SJ, Howley PM, editors. Annual Review of Pathology: Mechanisms of Disease, 6 (6th edn). Palo Alto: Annual Reviews. pp. 121–145.

    • Google Scholar
21. 1. Fujita M
    2. Urano T
    3. Horie K
    4. Ikeda K
    5. Tsukui T
    6. Fukuoka H
    7. Tsutsumi O
    8. Ouchi Y
    9. Inoue S

    (2002) Estrogen activates cyclin-dependent kinases 4 and 6 through induction of cyclin D in rat primary osteoblasts

    Biochemical and Biophysical Research Communications 299:222–228.

    https://doi.org/10.1016/S0006-291X(02)02640-2

    • PubMed
    • Google Scholar
22. 1. Gao L
    2. Tian M
    3. Zhao HY
    4. Xu QQ
    5. Huang YM
    6. Si QC
    7. Tian Q
    8. Wu QM
    9. Hu XM
    10. Sun LB
    11. McClintock SM
    12. Zeng Y

    (2016) TrkB activation by 7, 8-dihydroxyflavone increases synapse AMPA subunits and ameliorates spatial memory deficits in a mouse model of alzheimer's disease

    Journal of Neurochemistry 136:620–636.

    https://doi.org/10.1111/jnc.13432

    • PubMed
    • Google Scholar
23. 1. Gasser RW

    (2019) Long-term safety of bisphosphonates

    The Journal of Clinical Endocrinology and Metabolism 90:1897–1899.

    https://doi.org/10.1210/jc.2005-0057

    • Google Scholar
24. 1. Gordon MD
    2. Nusse R

    (2006) Wnt signaling: multiple pathways, multiple receptors, and multiple transcription factors

    Journal of Biological Chemistry 281:22429–22433.

    https://doi.org/10.1074/jbc.R600015200

    • PubMed
    • Google Scholar
25. 1. Gupta V
    2. Chitranshi N
    3. You Y
    4. Gupta V
    5. Klistorner A
    6. Graham S

    (2014) Brain derived neurotrophic factor is involved in the regulation of glycogen synthase kinase 3β (GSK3β) signalling

    Biochemical and Biophysical Research Communications 454:381–386.

    https://doi.org/10.1016/j.bbrc.2014.10.087

    • PubMed
    • Google Scholar
26. 1. Jang SW
    2. Liu X
    3. Yepes M
    4. Shepherd KR
    5. Miller GW
    6. Liu Y
    7. Wilson WD
    8. Xiao G
    9. Blanchi B
    10. Sun YE
    11. Ye K

    (2010) A selective TrkB agonist with potent neurotrophic activities by 7,8-dihydroxyflavone

    PNAS 107:2687–2692.

    https://doi.org/10.1073/pnas.0913572107

    • PubMed
    • Google Scholar
27. 1. Jiang M
    2. Wang T
    3. Yan X
    4. Liu Z
    5. Yan Y
    6. Yang K
    7. Qi J
    8. Zhou H
    9. Qian N
    10. Zhou Q
    11. Chen B
    12. Xu X
    13. Xi X
    14. Yang C
    15. Deng L

    (2019) A novel rhein derivative modulates bone formation and resorption and ameliorates Estrogen-Dependent bone loss

    Journal of Bone and Mineral Research 34:361–374.

    https://doi.org/10.1002/jbmr.3604

    • PubMed
    • Google Scholar
28. 1. Karner CM
    2. Long F

    (2017) Wnt signaling and cellular metabolism in osteoblasts

    Cellular and Molecular Life Sciences 74:1649–1657.

    https://doi.org/10.1007/s00018-016-2425-5

    • PubMed
    • Google Scholar
29. 1. Kauschke V
    2. Gebert A
    3. Calin M
    4. Eckert J
    5. Scheich S
    6. Heiss C
    7. Lips KS

    (2018a) Effects of new beta-type Ti-40Nb implant materials, brain-derived neurotrophic factor, acetylcholine and nicotine on human mesenchymal stem cells of osteoporotic and non osteoporotic donors

    PLOS ONE 13:e0193468.

    https://doi.org/10.1371/journal.pone.0193468

    • PubMed
    • Google Scholar
30. 1. Kauschke V
    2. Schneider M
    3. Jauch A
    4. Schumacher M
    5. Kampschulte M
    6. Rohnke M
    7. Henss A
    8. Bamberg C
    9. Trinkaus K
    10. Gelinsky M
    11. Heiss C
    12. Lips K

    (2018b) Effects of a pasty bone cement containing Brain-Derived neurotrophic Factor-Functionalized mesoporous bioactive glass particles on metaphyseal healing in a new murine osteoporotic fracture model

    International Journal of Molecular Sciences 19:3531.

    https://doi.org/10.3390/ijms19113531

    • Google Scholar
31. 1. Khosla S
    2. Hofbauer LC

    (2017) Osteoporosis treatment: recent developments and ongoing challenges

    The Lancet Diabetes & Endocrinology 5:898–907.

    https://doi.org/10.1016/S2213-8587(17)30188-2

    • PubMed
    • Google Scholar
32. 1. Kilian O
    2. Hartmann S
    3. Dongowski N
    4. Karnati S
    5. Baumgart-Vogt E
    6. Härtel FV
    7. Noll T
    8. Schnettler R
    9. Lips KS

    (2014) BDNF and its TrkB receptor in human fracture healing

    Annals of Anatomy - Anatomischer Anzeiger 196:286–295.

    https://doi.org/10.1016/j.aanat.2014.06.001

    • Google Scholar
33. 1. Kim JY
    2. Cheon YH
    3. Kwak SC
    4. Baek JM
    5. Yoon KH
    6. Lee MS
    7. Oh J

    (2014) Emodin regulates bone remodeling by inhibiting osteoclastogenesis and stimulating osteoblast formation

    Journal of Bone and Mineral Research 29:1541–1553.

    https://doi.org/10.1002/jbmr.2183

    • PubMed
    • Google Scholar
34. 1. Kim JH
    2. Kim N

    (2016) Signaling pathways in osteoclast differentiation

    Chonnam Medical Journal 52:12–17.

    https://doi.org/10.4068/cmj.2016.52.1.12

    • PubMed
    • Google Scholar
35. 1. Kokabu S
    2. Lowery JW
    3. Jimi E

    (2016) Cell fate and differentiation of bone marrow mesenchymal stem cells

    Stem Cells International 2016:1–7.

    https://doi.org/10.1155/2016/3753581

    • PubMed
    • Google Scholar
36. 1. Kong YY
    2. Yoshida H
    3. Sarosi I
    4. Tan HL
    5. Timms E
    6. Capparelli C
    7. Morony S
    8. Oliveira-dos-Santos AJ
    9. Van G
    10. Itie A
    11. Khoo W
    12. Wakeham A
    13. Dunstan CR
    14. Lacey DL
    15. Mak TW
    16. Boyle WJ
    17. Penninger JM

    (1999) OPGL is a key regulator of osteoclastogenesis, lymphocyte development and lymph-node organogenesis

    Nature 397:315–323.

    https://doi.org/10.1038/16852

    • PubMed
    • Google Scholar
37. 1. Krishnan V

    (2006) Regulation of bone mass by wnt signaling

    Journal of Clinical Investigation 116:1202–1209.

    https://doi.org/10.1172/JCI28551

    • Google Scholar
38. 1. Lacey DL
    2. Timms E
    3. Tan HL
    4. Kelley MJ
    5. Dunstan CR
    6. Burgess T
    7. Elliott R
    8. Colombero A
    9. Elliott G
    10. Scully S
    11. Hsu H
    12. Sullivan J
    13. Hawkins N
    14. Davy E
    15. Capparelli C
    16. Eli A
    17. Qian YX
    18. Kaufman S
    19. Sarosi I
    20. Shalhoub V
    21. Senaldi G
    22. Guo J
    23. Delaney J
    24. Boyle WJ

    (1998) Osteoprotegerin ligand is a cytokine that regulates osteoclast differentiation and activation

    Cell 93:165–176.

    https://doi.org/10.1016/S0092-8674(00)81569-X

    • PubMed
    • Google Scholar
39. 1. Langdahl B
    2. Ferrari S
    3. Dempster DW

    (2016) Bone modeling and remodeling: potential as therapeutic targets for the treatment of osteoporosis

    Therapeutic Advances in Musculoskeletal Disease 8:225–235.

    https://doi.org/10.1177/1759720X16670154

    • PubMed
    • Google Scholar
40. 1. Leder BZ

    (2017) Parathyroid hormone and parathyroid Hormone-Related protein analogs in osteoporosis therapy

    Current Osteoporosis Reports 15:110–119.

    https://doi.org/10.1007/s11914-017-0353-4

    • PubMed
    • Google Scholar
41. 1. Leibbrandt A
    2. Penninger JM

    (2008) RANK/RANKL: regulators of immune responses and bone physiology

    Annals of the New York Academy of Sciences 1143:123–150.

    https://doi.org/10.1196/annals.1443.016

    • Google Scholar
42. 1. Li J
    2. Yang M
    3. Lu C
    4. Han J
    5. Tang S
    6. Zhou J
    7. Li Y
    8. Ming T
    9. Wang ZJ
    10. Su X

    (2020) Tuna bone powder alleviates Glucocorticoid-Induced osteoporosis via coregulation of the NF-κB and wnt/β-Catenin signaling pathways and modulation of gut Microbiota composition and metabolism

    Molecular Nutrition & Food Research 64:e1900861.

    https://doi.org/10.1002/mnfr.201900861

    • PubMed
    • Google Scholar
43. 1. Libouban H
    2. Moreau MF
    3. Baslé MF
    4. Bataille R
    5. Chappard D

    (2003) Increased bone remodeling due to ovariectomy dramatically increases tumoral growth in the 5t2 multiple myeloma mouse model

    Bone 33:283–292.

    https://doi.org/10.1016/S8756-3282(03)00196-0

    • PubMed
    • Google Scholar
44. 1. Liu L
    2. Guo Y
    3. Wan Z
    4. Shi C
    5. Li J
    6. Li R
    7. Hao Q
    8. Li H
    9. Zhang X

    (2012) Effects of phytoestrogen α-ZAL and mechanical stimulation on proliferation, osteoblastic differentiation, and OPG/RANKL expression in MC3T3-E1 Pre-Osteoblasts

    Cellular and Molecular Bioengineering 5:427–439.

    https://doi.org/10.1007/s12195-012-0244-9

    • Google Scholar
45. 1. Liu X
    2. Obianyo O
    3. Chan CB
    4. Huang J
    5. Xue S
    6. Yang JJ
    7. Zeng F
    8. Goodman M
    9. Ye K

    (2014) Biochemical and biophysical investigation of the brain-derived neurotrophic factor mimetic 7,8-dihydroxyflavone in the binding and activation of the TrkB receptor

    Journal of Biological Chemistry 289:27571–27584.

    https://doi.org/10.1074/jbc.M114.562561

    • PubMed
    • Google Scholar
46. 1. Liu C
    2. Chan CB
    3. Ye K

    (2016a) 7,8-dihydroxyflavone, a small molecular TrkB agonist, is useful for treating various BDNF-implicated human disorders

    Translational Neurodegeneration 5:2.

    https://doi.org/10.1186/s40035-015-0048-7

    • PubMed
    • Google Scholar
47. 1. Liu YQ
    2. Hong ZL
    3. Zhan LB
    4. Chu HY
    5. Zhang XZ
    6. Li GH

    (2016b) Wedelolactone enhances osteoblastogenesis by regulating wnt/β-catenin signaling pathway but suppresses osteoclastogenesis by NF-κB/c-fos/NFATc1 pathway

    Scientific Reports 6:32260.

    https://doi.org/10.1038/srep32260

    • PubMed
    • Google Scholar
48. 1. Liu Q
    2. Lei L
    3. Yu T
    4. Jiang T
    5. Kang Y

    (2018) Effect of Brain-Derived neurotrophic factor on the neurogenesis and osteogenesis in bone engineering

    Tissue Engineering Part A 24:1283–1292.

    https://doi.org/10.1089/ten.tea.2017.0462

    • PubMed
    • Google Scholar
49. 1. Liu J
    2. Curtis EM
    3. Cooper C
    4. Harvey NC

    (2019) State of the art in osteoporosis risk assessment and treatment

    Journal of Endocrinological Investigation 42:1149–1164.

    https://doi.org/10.1007/s40618-019-01041-6

    • PubMed
    • Google Scholar
50. 1. Maïmoun L
    2. Brennan-Speranza TC
    3. Rizzoli R
    4. Ammann P

    (2012) Effects of ovariectomy on the changes in microarchitecture and material level properties in response to hind leg disuse in female rats

    Bone 51:586–591.

    https://doi.org/10.1016/j.bone.2012.05.001

    • PubMed
    • Google Scholar
51. 1. McGee-Lawrence ME
    2. Carpio LR
    3. Bradley EW
    4. Dudakovic A
    5. Lian JB
    6. van Wijnen AJ
    7. Kakar S
    8. Hsu W
    9. Westendorf JJ

    (2014) Runx2 is required for early stages of endochondral bone formation but delays final stages of bone repair in Axin2-deficient mice

    Bone 66:277–286.

    https://doi.org/10.1016/j.bone.2014.06.022

    • PubMed
    • Google Scholar
52. 1. Moon RT
    2. Kohn AD
    3. Ferrari GVD
    4. Kaykas A

    (2004) WNT and β-catenin signalling: diseases and therapies

    Nature Reviews Genetics 5:691–701.

    https://doi.org/10.1038/nrg1427

    • Google Scholar
53. 1. Newman DJ
    2. Cragg GM

    (2020) Natural products as sources of new drugs over the nearly four decades from 01/1981 to 09/2019

    Journal of Natural Products 83:770–803.

    https://doi.org/10.1021/acs.jnatprod.9b01285

    • PubMed
    • Google Scholar
54. 1. Ochs G
    2. Penn RD
    3. York M
    4. Giess R
    5. Beck M
    6. Tonn J
    7. Haigh J
    8. Malta E
    9. Traub M
    10. Sendtner M
    11. Toyka KV

    (2000) A phase I/II trial of recombinant methionyl human brain derived neurotrophic factor administered by intrathecal infusion to patients with amyotrophic lateral sclerosis

    Amyotrophic Lateral Sclerosis and Other Motor Neuron Disorders 1:201–206.

    https://doi.org/10.1080/14660820050515197

    • PubMed
    • Google Scholar
55. 1. Ozaki I
    2. Zhang H
    3. Mizuta T
    4. Ide Y
    5. Eguchi Y
    6. Yasutake T
    7. Sakamaki T
    8. Pestell RG
    9. Yamamoto K

    (2007) Menatetrenone, a vitamin K2 analogue, inhibits hepatocellular carcinoma cell growth by suppressing cyclin D1 expression through inhibition of nuclear factor kappaB activation

    Clinical Cancer Research 13:2236–2245.

    https://doi.org/10.1158/1078-0432.CCR-06-2308

    • PubMed
    • Google Scholar
56. 1. Pandey SN
    2. Kwatra M
    3. Dwivedi DK
    4. Choubey P
    5. Lahkar M
    6. Jangra A

    (2020) 7,8-Dihydroxyflavone alleviated the high-fat diet and alcohol-induced memory impairment: behavioral, biochemical and molecular evidence

    Psychopharmacology 237:1827–1840.

    https://doi.org/10.1007/s00213-020-05502-2

    • PubMed
    • Google Scholar
57. 1. Park J
    2. Hahm S-W
    3. Son Y-S

    (2011) Effects of cheonnyuncho (Opuntia humifusa) seeds treatment on the mass, quality, and the turnover of bone in ovariectomized rats

    Food Science and Biotechnology 20:1517–1524.

    https://doi.org/10.1007/s10068-011-0210-7

    • Google Scholar
58. 1. Phan QT
    2. Tan WH
    3. Liu R
    4. Sundaram S
    5. Buettner A
    6. Kneitz S
    7. Cheong B
    8. Vyas H
    9. Mathavan S
    10. Schartl M
    11. Winkler C

    (2020) Cxcl9l and Cxcr3.2 regulate recruitment of osteoclast progenitors to bone matrix in a medaka osteoporosis model

    PNAS 117:19276–19286.

    https://doi.org/10.1073/pnas.2006093117

    • PubMed
    • Google Scholar
59. 1. Raisz LG

    (2005) Pathogenesis of osteoporosis: concepts, conflicts, and prospects

    Journal of Clinical Investigation 115:3318–3325.

    https://doi.org/10.1172/JCI27071

    • Google Scholar
60. 1. Reid IR

    (2011) Bisphosphonates in the treatment of osteoporosis: a review of their contribution and controversies

    Skeletal Radiology 40:1191–1196.

    https://doi.org/10.1007/s00256-011-1164-9

    • PubMed
    • Google Scholar
61. 1. Ryoo HM
    2. Lee MH
    3. Kim YJ

    (2006) Critical molecular switches involved in BMP-2-induced osteogenic differentiation of mesenchymal cells

    Gene 366:51–57.

    https://doi.org/10.1016/j.gene.2005.10.011

    • PubMed
    • Google Scholar
62. 1. Sims NA
    2. Gooi JH

    (2008) Bone remodeling: multiple cellular interactions required for coupling of bone formation and resorption

    Seminars in Cell & Developmental Biology 19:444–451.

    https://doi.org/10.1016/j.semcdb.2008.07.016

    • PubMed
    • Google Scholar
63. 1. Sun CY
    2. Chu ZB
    3. She XM
    4. Zhang L
    5. Chen L
    6. Ai LS
    7. Hu Y

    (2012) Brain-derived neurotrophic factor is a potential osteoclast stimulating factor in multiple myeloma

    International Journal of Cancer 130:827–836.

    https://doi.org/10.1002/ijc.26059

    • PubMed
    • Google Scholar
64. 1. Takada I
    2. Kouzmenko AP
    3. Kato S

    (2009) Wnt and PPAR gamma signaling in osteoblastogenesis and adipogenesis

    Nature Reviews Rheumatology 5:442–447.

    https://doi.org/10.1038/nrrheum.2009.137

    • PubMed
    • Google Scholar
65. 1. Thoenen H
    2. Sendtner M

    (2002) Neurotrophins: from enthusiastic expectations through sobering experiences to rational therapeutic approaches

    Nature Neuroscience 5:1046–1050.

    https://doi.org/10.1038/nn938

    • PubMed
    • Google Scholar
66. 1. Walsh NC
    2. Gravallese EM

    (2010) Bone remodeling in rheumatic disease: a question of balance

    Immunological Reviews 233:301–312.

    https://doi.org/10.1111/j.0105-2896.2009.00857.x

    • PubMed
    • Google Scholar
67. 1. Wang J
    2. Yang J
    3. Cheng X
    4. Yin F
    5. Zhao Y
    6. Zhu Y
    7. Yan Z
    8. Khodaei F
    9. Ommati MM
    10. Manthari RK
    11. Wang J

    (2019) Influence of calcium supplementation against Fluoride-Mediated osteoblast impairment in vitro: involvement of the canonical wnt/β-Catenin signaling pathway

    Journal of Agricultural and Food Chemistry 67:10285–10295.

    https://doi.org/10.1021/acs.jafc.9b03835

    • PubMed
    • Google Scholar
68. 1. Yang X
    2. Karsenty G

    (2002) Transcription factors in bone: developmental and pathological aspects

    Trends in Molecular Medicine 8:340–345.

    https://doi.org/10.1016/S1471-4914(02)02340-7

    • PubMed
    • Google Scholar
69. 1. Zhang Z
    2. Liu X
    3. Schroeder JP
    4. Chan CB
    5. Song M
    6. Yu SP
    7. Weinshenker D
    8. Ye K

    (2014) 7,8-dihydroxyflavone prevents synaptic loss and memory deficits in a mouse model of alzheimer's disease

    Neuropsychopharmacology 39:638–650.

    https://doi.org/10.1038/npp.2013.243

    • PubMed
    • Google Scholar
70. 1. Zhang Z
    2. Zhang Y
    3. Zhou Z
    4. Shi H
    5. Qiu X
    6. Xiong J
    7. Chen Y

    (2017) BDNF regulates the expression and secretion of VEGF from osteoblasts via the TrkB/ERK1/2 signaling pathway during fracture healing

    Molecular Medicine Reports 15:1362–1367.

    https://doi.org/10.3892/mmr.2017.6110

    • PubMed
    • Google Scholar
71. 1. Zhang T
    2. Han W
    3. Zhao K
    4. Yang W
    5. Lu X
    6. Jia Y
    7. Qin A
    8. Qian Y

    (2019) Psoralen accelerates bone fracture healing by activating both osteoclasts and osteoblasts

    The FASEB Journal 33:5399–5410.

    https://doi.org/10.1096/fj.201801797R

    • PubMed
    • Google Scholar
72. 1. Zhang Z
    2. Hu P
    3. Wang Z
    4. Qiu X
    5. Chen Y

    (2020) BDNF promoted osteoblast migration and fracture healing by up-regulating integrin β1 via TrkB-mediated ERK1/2 and AKT signalling

    Journal of Cellular and Molecular Medicine 24:10792–10802.

    https://doi.org/10.1111/jcmm.15704

    • PubMed
    • Google Scholar
73. 1. Zhao X
    2. Mei L
    3. Pei J
    4. Liu Z
    5. Shao Y
    6. Tao Y
    7. Zhang X
    8. Jiang L

    (2017) Sophoridine from Sophora flower attenuates ovariectomy induced osteoporosis through the RANKL-ERK-NFAT pathway

    Journal of Agricultural and Food Chemistry 65:9647–9654.

    https://doi.org/10.1021/acs.jafc.7b03666

    • PubMed
    • Google Scholar
74. 1. Zhao X
    2. Ning L
    3. Xie Z
    4. Jie Z
    5. Li X
    6. Wan X
    7. Sun X
    8. Huang B
    9. Tang P
    10. Shen S
    11. Qin A
    12. Ma Y
    13. Song L
    14. Fan S
    15. Wan S

    (2019) The novel p38 inhibitor, pamapimod, inhibits osteoclastogenesis and counteracts Estrogen-Dependent bone loss in mice

    Journal of Bone and Mineral Research 34:911–922.

    https://doi.org/10.1002/jbmr.3655

    • PubMed
    • Google Scholar
75. 1. Zhao Z
    2. Xue F
    3. Gu Y
    4. Han J
    5. Jia Y
    6. Ye K
    7. Zhang Y

    (2021) Crosstalk between the muscular estrogen receptor α and BDNF/TrkB signaling alleviates metabolic syndrome via 7,8-dihydroxyflavone in female mice

    Molecular Metabolism 45:101149.

    https://doi.org/10.1016/j.molmet.2020.101149

    • PubMed
    • Google Scholar
76. 1. Zhou YM
    2. Yang YY
    3. Jing YX
    4. Yuan TJ
    5. Sun LH
    6. Tao B
    7. Liu JM
    8. Zhao HY

    (2020) BMP9 reduces bone loss in ovariectomized mice by dual regulation of bone remodeling

    Journal of Bone and Mineral Research 35:978–993.

    https://doi.org/10.1002/jbmr.3957

    • PubMed
    • Google Scholar

Author details

1. Fan Xue

   Department of Food Science and Nutrition, College of Biosystems Engineering and Food Science, Zhejiang Key Laboratory for Agro-Food Processing; Zhejiang Engineering Center for Food Technology and Equipment, Zhejiang University, Hangzhou, China

   Contribution

   Resources, Data curation, Formal analysis, Validation, Investigation, Visualization, Writing - original draft

   Competing interests

   No competing interests declared

   "This ORCID iD identifies the author of this article:" 0000-0003-0057-3792

2. Zhenlei Zhao

   Department of Food Science and Nutrition, College of Biosystems Engineering and Food Science, Zhejiang Key Laboratory for Agro-Food Processing; Zhejiang Engineering Center for Food Technology and Equipment, Zhejiang University, Hangzhou, China

   Contribution

   Resources, Formal analysis, Investigation, Writing - original draft

   Competing interests

   No competing interests declared

3. Yanpei Gu

   Department of Food Science and Nutrition, College of Biosystems Engineering and Food Science, Zhejiang Key Laboratory for Agro-Food Processing; Zhejiang Engineering Center for Food Technology and Equipment, Zhejiang University, Hangzhou, China

   Contribution

   Formal analysis, Investigation, Visualization

   Competing interests

   No competing interests declared

4. Jianxin Han

   Department of Food Science and Nutrition, College of Biosystems Engineering and Food Science, Zhejiang Key Laboratory for Agro-Food Processing; Zhejiang Engineering Center for Food Technology and Equipment, Zhejiang University, Hangzhou, China

   Contribution

   Formal analysis, Visualization

   Competing interests

   No competing interests declared

5. Keqiang Ye

   Department of Pathology and Laboratory Medicine, Emory University School of Medicine, Atlanta, United States

   Contribution

   Conceptualization, Resources, Supervision, Project administration, Writing - review and editing

   For correspondence

   kye@emory.edu

   Competing interests

   No competing interests declared

6. Ying Zhang

   Department of Food Science and Nutrition, College of Biosystems Engineering and Food Science, Zhejiang Key Laboratory for Agro-Food Processing; Zhejiang Engineering Center for Food Technology and Equipment, Zhejiang University, Hangzhou, China

   Contribution

   Conceptualization, Resources, Supervision, Funding acquisition, Project administration, Writing - review and editing

   For correspondence

   yzhang@zju.edu.cn

   Competing interests

   No competing interests declared

   "This ORCID iD identifies the author of this article:" 0000-0001-8533-4138

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